Don't forget that factories making the M1911 were working to capacity day and night. Machinery and machinists were straining to turn out all they could --- and other factories were "drafted" into service in an attempt to meet demand. Ever heard of an M1911 made by Singer Sewing Machine Company? Many companies who made typewriters, juke boxes, you name it, geared up to make various small arms. No stone was left unturned in the war effort.
Against this backdrop, it is easy to see how the revolver-making machinery and expertise at S&W and Colt would not be overlooked. Revolvers were easier to master than the M1911, and many US service men probably prefered them. IIRC, countries like England, Austrailia, and New Zealand had revolvers as their standard issue side arms anyway, so it was a natural to provide them with S&Ws and Colts chambered for their service round.